When tanks rumbled through Polish cities Dec. 13, 1981, to smash Solidarity, nobody could have imagined that the regime would have to resurrect the free trade union to rescue Poland from an economic and political crisis.

But, seven years later, that's exactly what's happening. With the opening of formal talks between Solidarity and the government last week, the banned union now has de facto recognition, something that would have been a miracle just a year ago.The authorities had to turn to Solidarity as a last resort because they feared losing control of an explosive situation caused by mismanagement, corruption and rampant inflation.

There are still plenty of hurdles to cross, however, before there is peace between the regime and Solidarity, the first free trade union in the Communist world.

Lech Walesa, leader of Solidarity since it was formed in 1980, has said repeatedly since the talks began Monday, "I didn't trust them in 1980; I don't trust them now."

Both sides have been surprisingly conciliatory in the talks as they try to seduce each other into an agreement. The government has indicated willingness to restore full legal status to the union outlawed in 1982, once agreement is reached in the talks.

The government and party strongly oppose any structure of Solidarity that would give it national power like it had in 1980 and 1981.

But the regime needs Solidarity's help in restructuring the economy if it is to gain popular support. So Walesa teases the government, saying Solidarity must have a national role if it is to be an effective partner.

Solidarity's decision to share responsibility is a big risk, because it could cause a split with radicals who are demanding total freedom for the union.

The regime, however, is in a far weaker position than in 1980 and 1981, since the party has become more isolated because of escalating dissatisfaction over economic problems.

Therefore, government spokesman Jerzy Urban now refers to Walesa as a "partner for the government" after years of describing the Nobel Peace Prize laureate as a paid CIA agent.

The international situation is also favorable for reform. Moscow is busy with its own internal problems and has shown no inclination to interfere with threats of invasion, as it did in 1980 and 1981 before Poland declared martial law.

The easing of Moscow's grip over Poland also means officials can no longer tell the nation that the Kremlin is blocking reform.

As the talks progress, other more conservative East European leaders are watching Poland uneasily, knowing the phantom of Solidarity will affect them sooner or later.